Swimming's world governing body FINA has declined to comment on the controversy surrounding British newspaper reports that China's three-time Olympic freestyle champion Sun Yang committed a doping violation last fall.

"FINA is aware of the reports in the Sunday Times and other media outlets regarding Chinese swimmer Sun Yang," said a statement released by FINA on Tuesday.

"In accordance with FINA's Anti-Doping Policy (FINA DC Rules 14.1.5 and 14.3.3) and the decision of the Doping Panel, FINA is not authorized to comment on the case. Moreover, FINA will not consider further speculation and hearsay on this matter."

FINA ruled on Jan 3 that Sun did not violate its anti-doping protocols.

The Times story, published last weekend, said Sun rejected a random out-of-competition doping test in his home city of Hangzhou on Sept 4, 2018, after questioning the identity of three testing officials－all of whom claimed to be employees of International Doping Tests and Management (IDTM).

IDTM is an independent organization authorized by swimming's global governing body FINA and the World Anti-Doping Agency (WADA) to conduct worldwide tests.

The Times story also said Sun destroyed one of his sealed blood samples with help from a security guard summoned by the swimmer's mother following a physical confrontation with the testers.

However, the Chinese Swimming Association defended Sun in a statement, describing the Times story as "untrue" and said his refusal to comply with the testing officials was "reasonable".

"As a result, the sample collection session initiated by IDTM on Sept 4, 2018, is invalid and void. Sun Yang did not commit an anti-doping rule violation under FINA DC 2.3 or FINA DC 2.5," the CSA quoted from the FINA decision.

Sun rejected the test because the testers could not provide documentation proving the process was legitimate.

His lawyer, Zhang Qihuai, subsequently revealed that two of the testers, who failed to show their IDTM certificates, were found to be untrained acquaintances of the main testing official.

Zhang has sent a letter to The Sunday Times, demanding an apology and retraction of the story.

On Monday, Britain's Daily Telegraph reported that FINA issued documentation to the IDTM to cover the group of testers, but Zhang argued in a closed-door hearing held in Lausanne, Switzerland on Nov 19 that each individual tester should have had separate certification.

Though FINA has cleared Sun of wrongdoing, WADA still has the right to lodge an appeal with the Court of Arbitration for Sport.

A spokesman for WADA told The Daily Telegraph on Monday that WADA is aware of the case and that it is following up accordingly.

Sun served a three-month suspension prior to the 2014 Asian Games after testing positive for stimulant trimetazidine, which he claimed he had been taking to treat a heart condition.

WADA had added the stimulant to its banned list earlier that year.